Improve "Defaults to" by putting to end of arg in docstring and ensuring backticks have proper spacing

[SamuelMarks]

If you prefer I can change all arguments to be how the popular Sphinx documentation generator parser works: https://sphinxcontrib-napoleon.readthedocs.io/en/latest/example_google.html

EDIT - Actually created a separate issue to discuss this #18944

Made much smaller and fewer changes than my previous (similar) PRs to improve chance of merging without controversy :)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 78.38%. Comparing base (1941c30) to head (b470eee).

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #18945   +/-   ##
=======================================
  Coverage   78.38%   78.38%           
=======================================
  Files         498      498           
  Lines       45520    45520           
  Branches     8393     8393           
=======================================
  Hits        35679    35679           
  Misses       8102     8102           
  Partials     1739     1739           

Flag	Coverage Δ
keras	78.22% <ø> (ø)
keras-jax	62.01% <ø> (ø)
keras-numpy	56.34% <ø> (ø)
keras-tensorflow	63.36% <ø> (ø)
keras-torch	62.03% <ø> (ø)

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[sachinprasadhs]

Please rebase the code to follow the latest code structure /keras/src/..

[SamuelMarks]

@sachinprasadhs No problem. Merged and resolved conflicts.